Broad-band transmit-receive tube for duplexers



H. HEINS June 14, 1955 -BROAD-BAND TRANSMIT-RECEIVE TUBE FOR DUPLEXERS 4 Sheets-Sheet 1 Filed March 19, 1954 INVENTOR. HAROLD HEINS BY "p flz ATTORNEY H. HEINS June 14, 1955 BROAD-BAND TRANSMIT-RECEIVE TUBE FOR DUPLEXERS 4 Sheets-Sheet 2 Filed March 19, 1954 |0 IO l3 FIG. 3

INVENTOR.

S Y m M D ,O L T /im m4? H June 14, 1955 H. HEINS 2,710,932

BROAD-BAND TRANSMIT-RECEIVE TUBE FOR DUPLEXERS Filed March 19, 1954- 4 Sheets-Sheet 3 l2 V I0 IO l3 26 I3 I0 I l9 l9 0 Y O Y O F l G. 5

INVENTOR. HAROLD HEINS BY yp4flr ATTORNEY June 14, 1955 H. HEINS 2,710,932

BROAD-BAND TRANSMIT-RECEIVE TUBE FOR DUFLEXERS Filed March 19, 1954 4 Sheets-Sheet 4 INVENTOR. HAROLD HElNS BY fizz" ATTORNEY United States Patent BROAD-BAND TRANSMlT-RECEIVE TUBE FOR DUPLEXERS Harold Heins, Marblehead, Mass., assignor to Bomac Laboratories Inc., Beverly, Masst, a corporation of Massachusetts Application March- 19, 1954, Serial No. 417,375

1 Claim. (Cl. 315-39) The present invention relates to broad-band balanced duplexers for radar systems, and more particularly to a broad-band transmit-receive tube for use with appropriate directional or short slot couplers to form a balanced duplexer.

The balanced duplexer as commonly employed in the radar systems has been fully discussed in Microwave Duplexers, by L. D. Smullin and C. G. Montgomery, McGraw-Hill Book Company, Inc., New York, 1948, pages 350 to 369 inclusive. ln this reference two specific types are described, namely the rat-race and magic-T type circuits. Another specific embodiment employs directional couplers in place of the rat-race or magic-T circuit and is described in detail in Patent No. 2,586,993, issued February 26, 1952 to Henry J. Riblet. A further improvement in the balanced duplexer art is described in an article by Henry I. Riblet entitled The Short-Slot Hybrid Junction, Proceedings of the I. R. E., vol. 40, February 1952, pages 180 to 184.

Both the directional coupler and short-slot hybrid junction balanced duplexers employ a pair of T-R gas switching tubes of the plural discharge gap type referred to as the 1363A which has excellent broad-band characteristics. Additional wave guide structure and mechanical holding devices are required for mounting these individual broad-band tubes in duplexer structure.

It is an object of the present invention to provide a transmit-receive gas switching tube which may be directly mounted between directional or short-slot couplers to form a simplified balanced duplexer without any intermediate wave guide structure.

Another object is to provide a broad-band transmitreceive gas switching tube having a common gas fill to assure equality of gas pressure and composition.

A further object is to provide a broad-band transmitreceive gas switching tube for use with directional or short-slot couplers, said tube having balanced electrical characteristics, initially and during life, essential for performance in balanced duplexers. 1

The objects, features and advantages of the presen invention Will be more readily appreciated after consideration of the following detailed description and accompanying drawings, in which:

Figure 1 is a perspective view of an illustrative embodiment;

Figure 2 is a detailed cross-sectional view along the line 22 in Figure 1;

Figure 3 is a detailed cross-sectional view along the line 3-3 in Figure 1;

Figure 4 is a perspective view of the embodiment shown mounted in Wave guide structure to form a balanced duplexer;

Figure 5 is a transverse cross-sectional view of a modification of the invention;

Figure 6 is an end view of another modification of the invention; and

Figure 7 is a perspective view of still another modification of the invention.

As shown in the drawings, Figure 1 illustrates the embodiment of the invention comprising a pair of similar rectangular wave guide sections 1 and 2 secured together in side by side relationship along the narrow wave guide wall. Hermetically sealed at each end of said joined wave guide sections are an input end flange 3 and output end flange 4; each of said flanges is provided with a plurality of mounting holes 5 for coupling the device in wave guide structure. which encompasses the joined wave guide sections thereby providing simple and efiicient means for coupling the tube in wave guide structure to form a balanced duplexer.

Each wave guide section 1 and 2 is provided with a pair of resonant windows hermetically sealed at the ends thereof comprising a frame 6 and 7 having a central aperture enclosed with a dielectric material as at 8 and 9. With the hermetically sealed Windows thus positioned, each wave guide section forms a sealed envelope which may be evacuated and filled with a suitable ionizable atmosphere.

Electromagnetic energy will be transmitted through the device by means of windows 8 and 9 when the power level is below the potential necessary to initiate a gaseous discharge. When the ionization potential of the gaseous atmosphere is exceeded a breakdown will take place and thereby change the impedance presented across the wave guide structure in the manner well known in the art.

Disposed at intervals of approximately one quarter of a wavelength and extending within each wave guide section 1 and 2 are a plurality of spaced metal plates 10 forming resonant irises 11. Within each iris are spaced resonant discharge gap electrodes 12, 13 and 14, 15 having convergent ends. Electrodes 13 and 15 have a threaded portion engaging a collar 16 and 17 hermetically sealed to the broad wall of wave guide sections 1 and 2. Nut 18 and 19 provides for retention of electrodes 13 and 15 in their desired position after axial adjustment to the desired resonant frequency.

Electrode 12 in each wave guide section is provided with a hollow passage and an ignitor electrode 20 is positioned within the hollow electrode. Ignitor electrode 20 is supported by a glass bead 21 sealed to a metal tube 22 which is in turn sealed to a ring 23 mounted on the wave guide envelope.

a current of approximately 100 to 200 microamperes.

As shown in Figure 3 a feature of the invention resides in the joining together of similar rectangular wave guide sections to form a common narrow wave guide Wall 25. In the illustrative embodiment, each wave guide wall forming the common wall 25 is approximately one half the thickness of the remaining wall structure. These dimensions can be determined by the desired frequency of operation: for example, at lower frequencies of approximately 6000 megacycles or less a double wall thickness may be employed, while at higher frequencies of from 6000 to 20,000 megacycles a single wall thickness is structurally preferred.

An aperture 26 is provided at an intermediate point of common wall 25 to facilitate simultaneous exhausting and filling of both sections with an ionizable atmosphere by means of tubulation 27. This aperture serves to maintain equality of gas pressure and composition in the wave guide sections. During operation this uniformity of the gas fill pressure and composition in the wave guide sections helps to insure uniformity of those T-R tube performance characteristics which are dependent on gas fill, such as leakage power, recovery time, are loss and ignitor voltage drop.

A complete duplexer assembly formed by employing an embodiment of my invention is shown in Figure 4 and has a broad frequency range of from 8500-9600 megacycles.

Each flange 3 and 4 is a unitary structurev Terminal cap 24 provides for connection to a suitable direct current voltage supply to provide The dual transmit-receive tube is mounted between two short-slot hybrid couplers 31 and 32 each being provided with special flanges 33 and 34 and gaskets to mate to the tube. The couplers are provided with input and output arms and can be obtained in either .E or H plane bends to provide the desired packaging for the overall equipment design. In the illustrative embodiment coupler 31 is provided with arm 35 connected .to the antenna and arm 36 which is connected to the transmitter. Coupler 32 is connected by means of arm- 37 .to the receiver and arm 38 to a dummy load.

During transmission high power signal energy entering the duplexer through arm 36 initiates a gaseous discharge across the input windows of tube 30 thereby effectively short circuiting coupler 31 and essentially all energy will be directed through arm 35 to the antenna. Since a perfect balance is not attainable in either the hybrid or tube sections, a small amount of power will pass through the tube 30. This power referred to as leakage power will pass through arm 38 to the dummy load.

During reception of the low power signal through arm 35 a 90 phase shift in each coupler 31 and 32 results in substantially complete transmission of the received signal to the receiver coupled to arm 37. The complete duplexer has been tested at 200 kilowatts of power with 1000 pulses per second and a 1.0 microsecond pulse width. In another test the duplexer operated over the broadband using 500 pulses per second and 2 microsecond pulse. watts have been employed with very low spike and fiat leakage power values, in the order of approximately .03 ergs spike energy or less and 7 microwatts peak leakage power or less. Recovery times of under 5 microseconds were recorded.

Data for low level voltage standing wave ratio presented to the antenna arm 35, the insertion loss in decibels from arm 35 to arm 37, the high level voltage .standing ratio presented to arm 36 during transmission and the overall isolation of the antenna arm 35 to transmitter arm 36 in terms of decibels is as follows:

Several modifications of the illustrative embodiment may be made. For example, a single ignitor electrode connection may be provided as shown in Figure 5. A wire electrode 40 extends into each hollow electrode 12 and is supported therein by a glass seal 41 insulating the conductor from the wave guide sections 1 and 2. Two

Transmitter powers of between 180 and 200 kilocurrent-balancing resistors 42 and 43 in series connect the wire electrodes to a common lead-in conductor wire 44. A cap 45 hermetically sealed to the wave guide sections encloses the resistors and electrode leads and supports the collar 46 and glass head 47 which in turn support the common lead-inrconduotor 44. Terminal cap 48 provides means for connection to a direct current voltage source which :in this embodiment would supply twice the current as the dual ignitor electrode structure, or approximately 200 to .300 microamperes.

Figures 6 and 7 illustrate a further modification of the invention in providing means for constructing compact duplexing systems. Figure 6 shows a triple tube arrangement wherein three sections of rectangular wave guide are joined in abutting relationship with a common apertured wall between said sections. Each section has an input resonant window 50, 51 and 52 and an ignitor electrode 53, 54, 55. A unitary mating flange 56 encompasses the three sections and provides means for mounting between appropriate couplers or wave guide structure.

Figure 7 provides a quadruple structure with four sections of wave guide 60 each sharing a top wall and side wall with an abutting section. Input flange 61 and output flange 62 are sealed at each end of said joined sections. In this embodiment plural ignitor electrodes 630i the side arm type extend into the narrow wall with one electrode in each section.

It will be apparent that other variations and modifications will occur to those skilled in the art. The invention makes possible the design of balanced duplexers of utmost simplicity and tubes constructed according to its teachings may be provided for any desired frequency range in the microwave region.

What is claimed is:

A broad-band transmit-receive tube for use in a balanced duplexer system, said tube comprising a plurality of mutually parallel rectangular wave guide envelope sections having 'board and narrow walls, said waveguide sections being joined together with each section sharing a common narrow wall throughout its length with an adjacent section, each of said wave guide envelope sections ehaving a dielectric window member hermetically sealed at the ends thereof, plural resonant discharge gap structures spaced .apart a quarter of a wavelength along the longitudinal axis within each of said wave guide envelope sections, said common narrow wall having an aperture therein for the passage of a similar ionizable atmosphere introduced into said wave guide sections to assure uniform balanced electrical characteristics of the duplexer system.

References Cited in the file of this patent UNITED STATES PATENTS 2,586,993 Riblet Feb. 26, 1952 2,617,957 Scott Nov. 11, 1952 2,625,668 Heins Jan. 13, 1953 

